1. Field of the Invention
The present invention concerns a combined gas/steam power station plant as described in the preamble to claim 1.
2. Discussion of Background
The concept "combined gas/steam power station plant"--referred to below as combined power station for short --is always understood to mean the interaction of at least one gas turbine group with at least one steam turbine circuit, the exhaust gases from the operation of the gas turbine group being passed through an exhaust heat steam generator (=exhaust heat boiler) in which the residual heat potential of these exhaust gases is used to generate the steam necessary for admission to the steam turbine. This additional steam power leads to a higher plant thermal efficiency. These combined power stations therefore have a very good conversion efficiency which is of the order of value of some 50-55%. One possibility of significantly increasing the efficiency of this plant can be an increase in the hot gas temperature. This introduces other disadvantages which have a negative effect on the efficiency of the plant and the economy of the electricity produced, i.e. the specific costs of the plant. It should therefore be noted that the preparation of a hot gas with a temperature of more than 1400.degree. C. inevitably involves an advance into a range in which the NO.sub.x emissions from this combustion increase abruptly, which, in turn, makes measures such as water or steam injection necessary. These measures substantially negate the efficiency improvement theoretically to be expected from the increase in temperature so that the associated gain in efficiency bears no relation to the expenditure required, quite apart from the fact that any increase in temperature involves expensive adaptations with respect to high quality materials and expensive arrangements for cooling, especially as regards the blading.